The real shades of gray (b&w film is a matter of heart) pt 1

Intro.

There are many resources about black and white film and its representation of color, perhaps one of the most important is Ansel Adams’ book The Negative, which I encourage every b&w photographer to read. That book was the door to a whole new experience in film, the challenge to understand and represent colors in monochrome, the incidence that the type of film emulsion and the filters you use have in the final image. But how did we end with the types of films that we have today? How was the evolution of monochrome film in its quest to represent “accurately” the colors that our eyes perceive?. Months later I found in LFI Magazine a series of articles by Torsten Andreas Hoffmann about composing in Back and White which provided me some light to those questions and finally lead me to write this post.

  1. Black and White films and their reaction to color.-

Black and white photography is based on the multiple representations of gray tonalities and how every single color provides its own shade of gray.

In order to better understand how each color is transformed into a gray tonality we should first understand how colors are perceived by our eye and then how it is captured by film.

Our perception of color.

Visible light is formed by electromagnetic radiation in the wavelengths between 390 – 710 nanometers (approximately). In other words visible light ranges between the invisible infrared light and ultraviolet light, everything in between (390 – 710nm wavelengths) are the colors that the human eye can perceive.

Image source: Wikipedia

Have you ever wondered the meaning of the spectral sensitivity chart that you find in the data sheet of your favorite b&w film? Well it turns out that black and white film is also sensitive to the different colors of the light spectrum, this is called spectral sensitivity.

Spectral sensitivity and the evolution of film

Through the history of b&w film, photographic emulsions were evolving in their sensitivity to the wavelength of colors in order to translate them into adequate shades of grey.

In the early days, the photographic emulsions were sensitive to blue, violet and ultraviolet light, but only slightly sensitive to green, and practically insensitive to the rest of the spectrum. In 1873 Hermann Wilhelm Vogel discovered dye sensitization which allowed photographic emulsions that were sensitive to green, yellow, orange and even red.

Types of photographic emulsions

Orthochromatic emulsion: a photographic emulsion with extended spectral sensitivity in the yellow-green region. They are high sensitivity to blue, generally correct sensitivity to green and bright yellow, but has too low sensitivity to orange and is practically insensitive to red, as it does not register wavelengths longer than approximately 560-600 nm (medium yellow to orange). Furthermore, orthochromatic emulsion has decreased sensitivity in the 500 nm area (pale blue) and so it reproduces brightness of blue colors more accurately. These films record red color darker than expected, they have special use in landscape photography because they render foliage luminously comparable to the eye perception, however you have to be careful if there are red reflecting surfaces such as rocks, tree bark and flowers because it will render white dark. It can also be used in portraits where it will emphasize skin and darken a ruddy complexion.

Currently, Rollei provides an orthochromatic film labeled as Rollei ORTHO 25, which is slow speed film (ISO 25) with a spectral sensitivity range 380 – 610nm

Ilford Ortho Plus Spectral Sensitivity

Note: the previous chart corresponds to Ilford Ortho Plus film which I believe is now discontinued

Isochromatic emulsion:  a photographic emulsion with increased sensitivity to yellow-green. They are excessively sensitive to violet and blue, but has generally correct sensitivity to yelow, slightly low sensitivity to green and registers wavelengths up to 620-650 nm (orange/red), so it’s not sensitive to deep red color.

Panchromatic emulsions: Panchromatic means sensitive to all colors of light. This is a photographic emulsion capable of recording red subjects, as its sensitivity range reaches wavelengths of 660-730 nm (orange/red to red). They have decreased sensitivity in the 490-540 nm area (blue to green). Early Panchromatic films were, however, still much too sensitive to blue light (what resulted e.g. in pictures with too bright sky and clouds invisible against white background), therefore required a yellow filter for correct representation of blue color brightness.

Panchromatic films first appeared in the early 1930’s. Further developments have been a matter of improving the linearity of spectral response. Kodak moved wholly to panchromatic by the mid-1950s.

Types of panchromatic emulsions

Originally there were three types of panchromatic films, Type A, B, and C.

Type A. It has increased blue sensitivity but reduced in red; it’s sometimes called orthopanchromatic. Examples of these films are Efke /Adox ISO 25 and ISO 50, and Fujifilm Acros 100 and Neopan SS 100. These films render blues lightly and greens, yellow and red darker.

Acros 100 spectral sensitivity

Note: the chart above corresponds to Fuji Acros 100, this is one of my favorites films, really high quality and surprisingly cheaper than other ISO 100 films.

Type B. Almost all modern panchromatic film fall in this category. They have a spectral response close to what the eye perceives; it can be made to match the eye’s response more exactly with a suitable yellow #8 filter. A typical panchromatic film is a bit too sensitive to red color as compared to yellow and green.

TriX spectral sensivity

Note: Trix is without question the most famous panchromatic film.

Type C. It has extended red sensitivity. Here we may found the Superpanchromatic which had additionally increased sensitivity to red colors (in the 620-680 nm) and generally a high speed (such as the Ilford Delta 400). One of the purposes of this type is to achieve a higher effective speed under rich tungsten illumination.

Delta 400 Spectral Sensitivity

Note: Above Delta 400.

Some special panchromatic films readily found today are:

Rollei Retro 80s which is a film with an extended red sensitivity that falls near into the infrared spectrum (approx. 780nm), this characteristic enhances its capacities in portrait and nude photography.

Kodak T-Max films which have reduced blue sensitivity, thus the effect of tilting the curve toward red, but not an increase in red response or extension into infrared, this enables the response of the film to be closer to the response of the human eye, blues may be recorded as slightly darker tones.

Closure

Nowadays, there are still a couple of different b&w emulsions to try, experiment, tame and love, unfortunately the price of film is increasing due to the lack of demand and the high cost of manufacture. The task is to look for the emulsion that matches your eye and your photographic style, stick to it and dominate it, many photographers love TriX and have been faithful to it for ages. Personally I like Fuji Acros 100 and Ilford HP5, followed by Kodak Trix and the now defunct Kodak Plus X, I am trying now Ilford FP4 as a substitute.

Now go out there and love some film.